DNR conducts long-term study

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By Molly Moser

The Iowa Department of Natural Resources Aquarium and Hatchery in Guttenberg remains open until mid-October this fall, while staff conducts testing at numerous sites along the river for a long-term resource-monitoring program.

At each of 35 randomly selected sites in pool 10 and 22 in pool 11, fisheries technician Kevin Hanson supervised testing of water quality, observations of habitat and vegetation, and the collection and documentation of fish in the area.

“In the mid-1980s, the Corps wanted to put an extra lock at a dam by St. Louis, so an environmental management program was set up to monitor the effects on the river after that was done,” said Hanson. For 25 years, DNR staff in pool 13 at Bellevue have made the same observations Hanson and his crews are making this fall. “In order to standardize our look at the river, we adopted their methods. We use their data sheets and send our data to them, so it gets compared with the rest of the sites in the Upper Mississippi River system.”

At each site, Hanson first takes a Secchi depth, using a black and white disc to determine water visibility. He measures the amount of oxygen in the water, and often finds it well above the level required to keep fish healthy. He takes the water temperature and answers a questionnaire about the surrounding vegetation, nearby land, and other water structures. 

Following the observations, Hanson drives the DNR’s electrofishing boat while two netters spend 15 minutes pulling temporarily stunned fish into the boat’s live well. Electrofishing is a common technique used by fisheries biologists to sample fish populations in fresh water, allowing them to more quickly learn details about fish populations, species composition, age distribution and presence of invasive species.

During a Sept. 12 visit at three different sites north of Lock and Dam 10, netters caught many small bluegill, indicating that this year’s spawn was successful for the fish. “All this high water’s not good for people, but it is good for fish. We are seeing the bluegill come back,” said Hanson.

Invasive species like the Asian carp and even a small clam were netted and measured along with native fish like perch, bass, gar, redhorse, shad and a variety of minnows. After measuring, fish were returned to their locations unharmed. 

Over the course of three 15-minute netting sessions on Sept. 12 between Guttenberg and Cassville, 192 fish were netted comprised of 24 different species. “This same thing is being done in Muscatine, and in 15 minutes they are sometimes coming up with only eight fish,” said Hanson. “This just shows the diversity we have here.”

For the second year, the Guttenberg aquarium did not hatch fish this spring. Hanson hopes the hatchery program in Guttenberg isn’t gone for good, but DNR staff have plenty to keep them busy nonetheless. In addition to the ongoing study, they’ve been contributing to educational efforts in Elgin and at the National Mississippi River Museum & Aquarium in Dubuque. In Dubuque, DNR staff meet with high school students to net for fish and turtles, discuss mussels, and more. 

After hurricane Katrina, fish from Guttenberg were shipped to an aquarium in New Orleans to help them restock – so similar projects could also be on the horizon once clean-ups from hurricanes Harvey and Irma begin to progress. 

Studies like the long-term resource monitoring program are often conducted in the fall because that’s when fish are healthiest. In October, the DNR will conduct a two-week survey of walleye and sauger, predatory fish that hunt in the dark, during night-fishing excursions. There are also overwintering samples taken in backwaters.

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